Field of the Invention
The present invention relates to a wireless communication system, and more particularly, to a method of performing scheduling for D2D (device to device) multicast communication in a wireless communication and an apparatus therefor.
Discussion of the Related Art
Recently, as a smartphone and a tablet PC (personal computer) are disseminated and a high-capacity multimedia communication is activated, mobile traffic is rapidly increasing. Hence, tendency of increase of the mobile traffic is expected to be doubled in every year in the future.
Since most of the mobile traffic is transmitted via a base station, communication service providers are facing a serious network load problem right now. In order to process the increasing traffic, the communication service providers have increased a network facility and have been commercializing such a next generation mobile communication standard capable of efficiently processing a great amount of traffic as mobile WiMAX, LTE and LTE-A. Yet, it is necessary for the service providers to have a different solution to cope with the amount of traffic to be rapidly increased. Hence, the service providers have started to take into consideration D2D communication.
When one or more user equipments are positioned at a distance adjacent to each other, the D2D (device-to-device) communication corresponds to a short-range communication scheme that delivers traffic via direct communication between the user equipments without passing through a base station. The D2D communication corresponds to a technology actively studied in recent years.
In case of performing the D2D communication, it may consider not only unicast communication of which two user equipments are directly communicating with each other via a single D2D link but also D2D multicast communication of which a single D2D user equipment delivers identical data to a neighboring plurality of D2D user equipments with a single transmission.
A representative service, which is expected to utilize the D2D multicast communication, may include an SNS (social network service), an advertising service and the like. The services are expected to be served by utilizing multimedia in the future.
In order to support a multimedia service including music, video streaming and the like in the D2D multicast communication, it is necessary to satisfy a demand on an average data transmission rate of a user, i.e., prescribed data transmission traffic per unit time. Since the multimedia service requires relatively high data transmission rate, efficient use of a radio resource is essential. Hence, it is required to have a scheduling method capable of securing an average data transmission rate of a D2D reception user equipment and efficiently utilizing a radio resource in the D2D multicast communication.
And, in order to perform the required scheduling method, the D2D reception user equipment may directly transmit channel state measurement information to a base station. In this case, it is not only necessary to maintain a strong point of the scheduling method while a resource necessary for transmitting the channel state measurement information is efficiently used by utilizing a structural merit of the D2D multicast communication (i.e., a group is formed in near distance and a signal is transmitted), it is also necessary to reduce scheduling complexity of a base station.
Moreover, in order to perform the required scheduling method, the base station should receive a report on channel state measurement information between all D2D reception user equipments and all D2D transmission user equipments belonging to a wireless communication system.
In doing so, since signaling overhead for transmitting the channel state measurement information is huge in a transmitting side and a base station, which is a receiving side, should perform scheduling using all channel state measurement information, it is necessary to reduce an amount of the channel state measurement information which is transmitted to perform the scheduling.